Fix author attachment field (#15065)

# Migrate Attachment Author to CreatedBy Field

**Twill Task**: https://twill.ai/twentyhq/ENG/tasks/7

## Summary

This PR implements a migration to transition the `Attachment` object
from using an `author` relation field to using the standard `createdBy`
field, addressing issue
https://github.com/twentyhq/core-team-issues/issues/1594.

## Changes

- **Added migration command**
(`1-8-migrate-attachment-author-to-created-by.command.ts`):
- Migrates existing attachment data to use `createdBy` instead of
`author`
- Ensures data integrity during the transition to the standard field
pattern

- **Updated Attachment workspace entity**:
  - Added `createdBy` relation field to the `Attachment` standard object
  - Registered new field ID in `standard-field-ids.ts` constants

- **Integrated migration into upgrade pipeline**:
  - Added migration module for version 1.8
  - Registered in the main upgrade version command module

This change aligns the `Attachment` object with Twenty's standard field
conventions by using the built-in `createdBy` field instead of a custom
`author` field.

---

Fixes https://github.com/twentyhq/core-team-issues/issues/1594

---------

Co-authored-by: Twill <agent@twill.ai>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Félix Malfait <felix.malfait@gmail.com>
Co-authored-by: Félix Malfait <felix@twenty.com>

CLAUDE.md

@@ -31,7 +31,7 @@ npx nx storybook:build twenty-front         # Build Storybook
 npx nx storybook:serve-and-test:static twenty-front     # Run Storybook tests
 
 
-When testing the UI end to end, click on "Continue with Email" and use the prefilled credentials. 
+When testing the UI end to end, click on "Continue with Email" and use the prefilled credentials.
 ```
 
 ### Code Quality
@@ -68,7 +68,7 @@ npx nx run twenty-server:database:migrate:prod # Run migrations
 npx nx run twenty-server:typeorm migration:generate src/database/typeorm/core/migrations/[name] -d src/database/typeorm/core/core.datasource.ts
 
 # Sync metadata
-npx nx run twenty-server:command workspace:sync-metadata -f
+npx nx run twenty-server:command workspace:sync-metadata
 ```
 
 ### GraphQL
@@ -149,4 +149,4 @@ IMPORTANT: Use Context7 for code generation, setup or configuration steps, or li
 - `nx.json` - Nx workspace configuration with task definitions
 - `tsconfig.base.json` - Base TypeScript configuration
 - `package.json` - Root package with workspace definitions
-- `.cursor/rules/` - Development guidelines and best practices
+- `.cursor/rules/` - Development guidelines and best practices